Mathematical communication has been emphasized not only as the process of learning mathematics but also as the objective of mathematics education. However, little studies have been conducted with regard to what to consider and how to implement in the actual classroom for promoting mathematical communication. Given this background, this paper implemented a mathematics instruction in each of 2nd, 4th, and 6th grade classrooms in which specific learning objectives were considered to promote discourse-based mathematical communication. It then analyzed the degree by which such learning objectives were achieved and the linguistic interactions between the teacher and students in each classroom. This paper finally provided issues and suggestions for effective discourse-based instruction in mathematics classroom by analyzing similarities and differences among the three classrooms.